1. Field of the Invention
The present invention relates to an optical film, and a polarizing plate and a liquid crystal display device each using the optical film.
2. Description of the Related Art
With the remarkable progress in the information industry, a display device is utilized in various places. In particular, a liquid display device is making striking progress and is mounted in various instruments. In these liquid crystal display devices, stability of display quality in the installed environment is an important matter.
The polarizing plate used in the liquid crystal display device is usually produced by sandwiching a polarizer between two protective films, and triacetyl cellulose (TAC) is preferably used as the polarizing plate protective film. However, humidity condition for a long time, sometimes causes a problem that light leakage or the like is generated and the display quality cannot be maintained.
On the other hand, a polymer having an alicyclic structure is excellent in the transparency, heat resistance and chemical resistance and less absorbs moisture and therefore, its use as a polarizing plate protective film is known. The above-described durability is enhanced as compared with the case using TAC, but this method has a problem that since the polymer having an alicyclic structure does not absorb an ultraviolet ray at a wavelength longer than 300 nm, the polarizing plate protective film itself deteriorates due to an ultraviolet ray or its underlayer such as polarizer, color filter and liquid crystal molecule deteriorates.
In order to prevent deterioration by an ultraviolet ray, studies are being made to cut the ultraviolet ray. As regards the method therefor, a technique of incorporating an ultraviolet absorbent into a polymer film having an alicyclic structure is disclosed (see, JP-A-2002-249600 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”))